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What is cancer?

Broadcast Date: Jan. 22, 1956

"Like a well-organized community, the human body has millions of specialized cells who work for a living," explains this 1956 television clip. The law-abiding cells in the community know when to stop growing. But cancer cells are like "outlaws" — they don't do any work, they greedily steal resources and grow like crazy, and then their descendents move to other areas of the body to start new "outlaw" colonies. "Why do cancer cells break the law? That's what thousands of scientists are trying to find out."

What is cancer?

• Cancer is an ancient disease not restricted to humans, according to the 1995 U.S.-published book Cancer Wars by Robert N. Proctor: "Evidence of tumours has been found in dinosaur bones more than a hundred million years old and in human tissues of Egyptian mummies dating back four or five millennia."
• The word cancer was derived from the Ancient Greek word karkinos (or carcinoma), which meant crab. The Greek physician Hippocrates (460-377 B.C.) gave cancer its name because of the crab-like appearance of a tumour.

• Throughout history, a variety of causes have been blamed for cancer. The Ancient Egyptians believed gods caused it. And humoural theory — that cancer (as well as most illnesses) was caused by an imbalance of humours, or bodily fluids — was widely believed to be a cause from the Middle Ages until the 18th century.

• By the 18th century, scientists and physicians were putting more emphasis on environmental causes for cancer, including exposure to harmful substances. In 1775, it was discovered that overexposure to chimney soot and tar in chimney sweeps in England caused cancers of the scrotum (called "soot wart").

• By the mid-20th century, scientists determined that cancer could be hereditary. As well, they discovered that exposure to chemicals, radiation and viruses could damage the body's building blocks by creating mutations in the DNA. Those mutated DNA sequences often lead to cancer.

• According to the American Cancer Institute, cancer typically forms as a solid tumour. But some cancers — like leukemia — don't form tumours. Instead, these cancer cells involve the blood and blood-forming organs. They circulate and grow through various tissues.

• The most prevalent types of cancers vary widely from country to country, and they've changed throughout history. Thanks to the rise of industrialization and the increase in tobacco smoking in North America throughout the 20th century, for instance, lung cancer rates have risen greatly. "In 1900, lung cancer was a very rare disease; today, it is the second-largest cause of death in industrial nations," Robert N. Proctor wrote in 1995.

• In Canada today (2005), the most commonly diagnosed forms of cancer are prostate cancer for men (an estimated 20,100 new diagnoses and 4,200 deaths in 2004), and breast cancer for women (an estimated 21,200 new diagnoses and 5,200 deaths in 2004). For both sexes, the leading cause of cancer death is lung cancer. In 2004, approximately 21,700 Canadians were diagnosed with lung cancer, and approximately 18,900 died of it.

• As life expectancies increase cancer rates will increase, since cancer primarily afflicts older people. The Canadian Cancer Society says that among men, 75 per cent of new cancer cases and 82 per cent of cancer deaths occur in men older than 60. Among women, 63 per cent of new diagnoses and 78 per cent of cancer deaths occur in women older than 60.

• Based on incidence rates from 2004, the Canadian Cancer Society says 38 percent of women and 43 per cent of men will develop cancer at some point during their lifetimes. Mortality rates vary depending on the type of cancer, but according to Canada's Cancer Research Society, mortality rates have begun to decline overall in recent years. The areas showing the greatest improvements in survival rates are stomach, bladder, Hodgkin's, testicular, breast and cervical cancer.

What is cancer?

Medium: Television

Program: Newsmagazine

Broadcast Date: Jan. 22, 1956

Narrator: Rex Loring

Duration: 1:22

Last updated:
March 7, 2005